This study aimed to investigate the potential of three bioamendments (rice husk biochar, wheat straw biochar, and spent mushroom compost) to enhance microbial degradation of crude oil in saline soil. A soil microcosm experiment was conducted, comparing the response of soil microorganisms to crude oil under saline (1 % NaCl) and non-saline conditions. The soils were amended with different bioamendments at varying concentrations (2.5 % or 5 %), and degradation rates were monitored over a 120-day period at 20 °C. The results showed that the bioamendments significantly influenced the degradation of total petroleum hydrocarbons (TPH) in both non-saline and saline soils by 67 % and 18 % respectively. Non-saline soils exhibited approximately four times higher TPH biodegradation compared to saline soils. Among the bioamendments, rice husk biochar and spent mushroom compost had the greatest impact on biodegradation in saline soil, while wheat straw and rice husk biochar combined with spent mushroom compost showed the most significant effects in non-saline soil. The study also revealed that the bioamendments facilitated changes in the microbial community structure, particularly in the treatments with rice husk biochar and wheat straw biochar. Actinomycetes and fungi were found to be more tolerant to soil salinity, especially in the treatments with rice husk biochar and wheat straw biochar. Additionally, the production of CO₂, indicating microbial activity, was highest (56 % and 60 %) in the treatments combining rice husk biochar or wheat straw biochar with spent mushroom compost in non-saline soil, while in saline soil rice husk biochar treatment (50 %) was the highest. Overall, this research demonstrates that the application of bioamendments, particularly rice husk biochar and wheat straw biochar combined with spent mushroom compost, can effectively enhance the biodegradation of crude oil in saline soil. These findings highlight the potential of such bioamendments as green and sustainable solutions for soil pollution, especially in the context of climate change-induced impacts on high-salinity soils, including coastal soils.

This study evaluated the efficacy of using Tween 80 surfactant (TW80) and food-waste anaerobic digestate fibre (FWAD) as soil amendments for the remediation of wetlands contaminated by crude oil. A 112-day mesocosms experiment was carried out to simulate hydrocarbon degradation under typical acidified wetland conditions. Soil was spiked with 50,000 mg kg⁻¹ crude oil and TW80 and FWAD were added to mesocosms at 10%, 20% and 30% w/w. The soil basal respiration, microbial community dynamics, environmental stress, alkanes, and PAHs degradation were monitored throughout the mesocosm experiment. Amending the mesocosms with FWAD and TW80 enabled the recovery of the soil microbial activities. This was evidenced by soil basal respiration which was the highest in the 30% FWAD and 30% TW80 mesocosms and translated into increased degradation rate of 32% and 23% for alkanes, and 33% and 26% for PAHs compared to natural attenuation, respectively. Efficient total hydrocarbon degradation was achieved in soil mesocosms with 30% FWAD and 30% TW80 at 90% and 86.8%, respectively after 49 days. Maize seed germination results showed significant improvement from 29% to over 90% following the FWAD and TW80 treatment.

Existing soil remediation approaches are lacking in cost-effectiveness, environmental impacts or societal acceptance. Environmental remediation techniques are often characterized by considerable time requirements and may leave residual effects on natural ecosystems, thereby potentially compromising net environmental benefits. This study investigated the oil adsorption capacity of aerogels produced from waste orange peels. Aerogels are highly porous three-dimensional materials made from organic and inorganic materials, with low density and high adjustable specific surface area. Orange peel aerogel was produced from waste orange peels using combined methods of physical, chemical, and thermal modification processes and was dried using the freeze-drying method. Adsorption and reusability tests were conducted after characterization of the aerogel. Surface characterization of the orange peel aerogel indicated it has an ultra-light density of 0.010417 g/cm³, high porosity of 99%, and a measured contact angle of 102°. An adsorption experiment was conducted with sandy and clay soils, and the maximum oil adsorption capacities of the orange peel aerogel were 13.55 mg/g and 9.60 mg/g for sandy and clay soils respectively. High oil adsorption capacity was shown by the produced aerogel and was attributed to its ultra-light density of 0.010417 g/cm³ and high porosity of 99%. In conclusion, the higher oil adsorption capacity of the orange peel aerogel in sandy soil compared with clay soil indicated that soil texture and aerogel properties influenced its oil remediation capacity. The reusability test in three adsorption trials indicated that orange peel aerogel is a sustainable material for the remediation of oil-contaminated soil.